1. 1-2 How Scientists Work (Experimental Design)
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TN State Standards
Learning Targets
CLE 3210.Inq.1
CLE 3210.Inq.2
CLE 3210.Inq.4
CLE 3210.Inq.5
I can:
Write a hypothesis in the correct form
Identify the parts of a controlled experiment
Use context clues to indentify different variables
Identify complete vs. incomplete conclusions.
Identify the parts of experiments given examples
Learning Goal
Analyze the components of a properly designed scientific investigation.
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Science
Observation
Hypothesis
Data
Dependent Variable
Independent Variable
Biology
Cell
Homeostasis
Sexual Reproduction
Asexual Reproduction
Metabolism
Microscope
Theory
DNA
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5. Designing an Experiment
An experiment is a meaningful way to test a hypothesis.
This process of testing a hypothesis includes:
Asking a question
Forming a hypothesis
Setting up a controlled experiment
Recording and analyzing results
Drawing a conclusion
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Asking a Questions
The experimental process begins by observing the world and asking questions about natural events(phenomena)
Forming a Hypothesis
A hypothesis state what the experimentor thinks is going to happen. (Written as and “if” “then” statement.)
If (the independent variable) is (increased, decreased, changed, etc.), then (the dependent variable) will (increase, decrease, change, etc.)
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7. Designing an Experiment
Setting Up a Controlled Experiment
Whenever possible, a hypothesis should be tested by an experiment in which only one variable is changed at a time. All other variables should be kept unchanged, or controlled
The variable that is deliberately changed is called the independent (manipulated) variable. It will be the cause of the changes you measure.
The variable that is observed and that changes in response to the manipulated variable is called the dependent (responding) variable. It will be the effect of the action of the you took with the other variable
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8. Setting Up a Controlled Experiment
Experimental Layout
Each experiment (lab) must consist of these parts:
Title: Identified the IV and DV. Includes the word Effect of or On
Hypothesis: States how you think the IV affects the DV.
Materials: List of materials needed in the experiment.
Procedure: List of the actions taking in the experiment.
Data Tables: Recorded the out come of experimental and control groups. Each table must have a title.
Conclusions: Explain the results and finding of the experiment
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9. Designing an Experiment
Recording Data and Analyzing Results
Data includes all observations and measurement recorded from an experiment.
Sometimes drawings are used to record certain kinds of observations. Researchers use computers to record their work. Computers are very useful in creating tables, charts, graphs and models from experimental data.
Tables & graphs are useful in identifying trends or patterns in the experiment data.
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10. Designing an Experiment
Drawing a Conclusion
The conclusion( in paragraph form) contains:
Description of the experiment
Discussion of the major findings,
Explanation of the findings,
Recommendations for further study
Scientist share their findings in journals so that other researchers can repeat their experiment and extend their conclusions.
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11. When Experiments Are Not Possible
It is not always possible to do an experiment to test a hypothesis. For example:
Wild animals must be observed without disturbing them.
Ethical/Moral considerations prevent some experiments.
By carefully planning alternative investigations, scientists can discover reliable patterns that add to scientific understanding.
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How a Theory Develops
As evidence from numerous investigations builds up, several related hypothesis may join to create a scientific theory.
In science, the word theory applies to a well-tested explanation that unifies a broad range of observations. No theory is considered absolute truth.
As new evidence is uncovered, a theory may be revised or replaced by a more useful explanation
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13. Designing an Experiment
Experimental Design in History
Many years ago, people wanted to know how living things came into existence. They asked:
How do organisms come into being?
Several Scientists Contributed to Answering this question
Francesco Redit (1668)
John Needham (1700)
Lazzaro Spallanzani (1700)
Louis Pastuer (1800)
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14. Designing an Experiment
Forming a Hypothesis
One early hypothesis was spontaneous generation, or the idea that life could come from nonliving matter. For example, most people thought that maggots spontaneously appeared on meat.
In 1668, Redi proposed a different hypothesis: that maggots came from eggs that flies laid on meat.
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Redi’s Experiment
Observation:
Hypothesis:
Procedure:
Control group
Independent Variable
Dependent Variable
Conclusion
Flies land of meat that is left uncovered. Later, maggots appear on the meat.
Flies produce maggots
Uncovered jars
Gauze that keeps flies away from meat
Whether maggots appear
Maggots form only when flies come in contact with meat. Spontaneous generation did not occur.
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16. Repeating Investigations
Scientists repeat experiments to be sure that the results match those already obtained.
Needham's Test of Redi's Findings
Needham challenged Redi’s results by claiming that spontaneous generation could occur under the right conditions.
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Target Check
1. Is this a good hypothesis, "Garlic adds health benefits to food.”
2. Why is this not a good experiment, “Measuring the rate of oxidation by leaving your bike out in the rain.”
3. Identify the variables in this statement, “The effect of nutrient deficiency on fiber strength in cotton plants.”
4. A good conclusion contains: an description, discussion explanation, & ____________.
1. No, it is not written as an “if/then” statement.
2. It does not have a control group.
3. IV-nutrient deficiency, DV- fiber strength
4. recommendations for further study.
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18. Repeating Investigations
Needham’s Test of Redi’s Findings
Needham sealed a bottle of gravy and heated it.
After several days, the gravy was swarming with microorganisms.
Needham concluded that these organisms came from the gravy by spontaneous generation.
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19. Repeating Investigations
Spallanzani's Test of Redi's Findings 
Gravy is boiled.
Gravy is boiled.
Spallanzani’s experiment showed that microorganisms will not grow in boiled gravy that has been sealed but will grow in boiled gravy that is left open to the air. Interpreting Graphics What variable was controlled in this experiment?
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20. Repeating Investigations
Spallanzani's Test of Redi's Findings 
Flask is open.
Flask is sealed.
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21. Repeating Investigations
Spallanzani's Test of Redi's Findings 
Gravy is teeming with microorganisms.
Gravy is free of microorganisms.
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22. Repeating Investigations
Pasteur's Test of Spontaneous Generation
Louis Pasteur conclusively disproved the hypothesis of spontaneous generation.
Pasteur showed that all living things come from other living things.
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23. Repeating Investigations
Pasteur’s Experiment
Broth is free of microorganisms for a year.
Curved neck is removed.
Broth is teeming with microorganisms.
Pasteur’s experiment showed that boiled broth would remain free of microorganisms even if air was allowed in, as long as dust and other particles were kept out.
Broth is boiled
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24. Repeating Investigations
The Impact of Pasteur’s Work
Pasteur saved the French wine industry, which was troubled by unexplained souring of wine.
He saved the silk industry, which was endangered by a silkworm disease.
He began to uncover the nature of infectious diseases, showing that they were the result of microorganisms.
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